Method for integrating a further bus subscriber into a bus system, and bus system for integrating a further bus subscriber therein

ABSTRACT

A method for integrating a further bus subscriber into a bus system, and a bus system, having a master module and subscribers disposed in series, includes the temporally consecutive method steps: in a first method step, the further bus subscriber transmits a data packet to the master module in order to log in to the master module, in a second method step, a bus subscriber disposed between the further bus subscriber and the master module stops the data packet and checks whether the bus system has already received a release, in a third method step, the first bus subscriber forwards the data packet to the master module if the bus system has not yet received a release, or in a third, in particular an alternative, method step, if the bus system has already received a release, the bus subscriber stores the data packet and waits until the release of the bus system is revoked and after the release has been revoked, forwards the stored data packet to the master module.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/098,589, which is the national stage of PCT/EP2017/025017,having an international filing date of Feb. 2, 2017, and claims priorityto Application No. 10 2016 005 313.5, filed in the Federal Republic ofGermany on May 2, 2016, each of which is expressly incorporated hereinin its entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a method for integrating a further bussubscriber into a bus system, and to a bus system.

BACKGROUND INFORMATION

German Published Patent Application No. 10 2005 056 294 describes amethod for allocating addresses to bus subscribers of a bus system, anda plant.

European Published Patent Application No. 1 124 351 describes acommunications protocol for nodes of a daisy chain.

German Published Patent Application No. 102 15 720 describes a data busnetwork.

European Published Patent Application No. 0 807 887 describes a methodfor addressing a number of peripheral modules of the central unit in aBUS line system.

German Published Patent Application No. 196 47 668 describes a slavestation, master station, BUS system, and a method for operating a BUSsystem.

SUMMARY

Example embodiments of the present invention provide a method forintegrating a further bus subscriber into a bus system and a bus system,in which the security is to be improved.

According to an example embodiment of the present invention, a methodfor integrating a further bus subscriber into a bus system, including amaster module and bus subscribers disposed in series, includes thefollowing temporally consecutive method steps: in a first method step,the further bus subscriber sends a data packet to the master module inorder to log in to the master module, in a second method step, a bussubscriber disposed between the further bus subscriber and the mastermodule stops the data packet and checks whether the bus system hasalready received a release, and in a third method step, the bussubscriber forwards the data packet to the master module if the bussystem has not yet received a release, or in a third, in particular analternative, method step, if the bus system has already received arelease, the bus subscriber stores the data packet and waits until therelease of the bus system is revoked, and after the release was revoked,forwards the stored data packet to the master module.

This has the advantage that a further bus subscriber, in particular abus subscriber that requires a longer period of time for the activation,is easily able to be integrated into the bus system retroactively.

In the production mode, i.e. after a granted release, no bus subscribermay be admitted to the bus system.

The admission to the bus system may be blocked with the aid of the bussubscriber situated between the master module and the further bussubscriber, so that the loading of the master module is reduced. Thisimproves the security.

The further bus subscriber may be automatically admitted to the bussystem in a new startup of the bus system.

The master module may ask the bus subscribers to log in to the mastermodule in order to initialize the bus system, and in a following methodstep, a first bus subscriber disposed downstream from the master modulemay log in to the master module, and in a subsequent method step, thefirst bus subscriber may wait for a predefined period of time to seewhether a second bus subscriber downstream from the first bus subscriberlogs in to the master module. This has the advantage that the bussubscribers reduce the loading of the master module. This improves thesecurity.

The predefined period of time may be adaptable to the bus subscribers,so that there is a sufficient wait to allow a bus subscriber that needsa longer period of time for the activation to be logged in securely aswell.

The first bus subscriber may close the bus system if no second bussubscriber logs in to the master module within the predefined period oftime. This has the advantage that the bus system automaticallyinitializes itself with the aid of the present method. The bus systemrecognizes which one is the bus subscriber most remote from the mastermodule, and this bus subscriber automatically closes the bus system.This relieves an operator of the bus system inasmuch as the operatordoes not have to connect a terminating impedance within the system. Thesecurity is therefore improved.

A second bus subscriber may log in to the master module within thepredefined period of time and may wait a further predefined period oftime to see whether a third bus subscriber disposed downstream from thesecond bus subscriber logs in to the master module, and the second bussubscriber may close the bus system if no third bus subscriber logs into the master module within the further predefined period of time. Thishas the advantage that the bus system automatically initializes itselfwith the aid of the present method. The bus system recognizes which oneof the bus subscribers is the one most remote from the master module,and this bus subscriber automatically closes the bus system. Thisrelieves an operator of the bus system inasmuch as the operator does nothave to connect a terminating impedance within the system. This improvesthe security.

The release may be granted and/or revoked by a control superordinate tothe master module. This has the advantage that with the aid of therelease, the bus system obtains an external release in an additionalmethod step after a successful initialization. Only after the releasedoes the bus system transition to a production mode in which the bussubscribers are controlled by the master module.

The following temporally successive method steps may be carried out forthe allocation of addresses to the bus subscribers: in a method step,the master module allocates a first address to a first bus subscriberand transmits this first address to the first bus subscriber, the firstaddress in particular being a natural number n, the first address inparticular being 0 or 1, in a following method step, the first bussubscriber increments the first address by one and allocates it to asecond bus subscriber as the second address and transmits this secondaddress to the second bus subscriber, the second address in particularbeing the natural number (n+1), and in a further method step, the secondbus subscriber logs in to the master module with its second address.

This has the advantage that the assignment of the addresses to the bussubscribers takes place automatically. As a result, the initializationof the bus system is able to be executed in a secure and rapid manner.

During the addressing, a data packet may pass an inactive bus subscriberso that the next active bus subscriber of the bus system receives theaddress and uses it to log in to the master module.

In a fourth method step, the second bus subscriber may increment thesecond address by one and may allocate this address to a third bussubscriber as the third address and may transmit this third address tothe third bus subscriber, the third address in particular being thenatural number (n+2), and in a fifth method step, the third bussubscriber may log in to the master module using its third address. Thishas the advantage that each bus subscriber, in particular each activebus subscriber, is automatically able to be addressed with the aid ofthe present method.

The address m may be allocated to an m^(th) bus subscriber in a furthermethod step, and the m^(th) bus subscriber may log in to the mastermodule using the address m, m being a natural number, and m inparticular being unequal to n, m in particular being equal to 15, andthe m^(th) bus subscriber may allocate the address m to a bus subscriberdownstream from the m^(th) bus subscriber, and may transmit the addressm to the downstream bus subscriber, the m^(th) bus subscriber inparticular not incrementing the address, (m−1) being the maximallypossible number of bus subscribers in the bus system. This has theadvantage that the number of the bus subscribers is able to be limited.Data packets do not become too long in this manner, and the transmissionspeed is improved. The number of bus subscribers may be automaticallyrestricted.

The master module may abort the method and may transmit an error reportwhen a bus subscriber using the address m logs in to the master module.This has the advantage that the bus system automatically recognizes whentoo many bus subscribers are logging in. The error report may be sent toa superordinate control. The master module may generate a warningsignal, in particular a warning tone or a warning light.

The following temporally successive method steps may be carried out forthe emergency shutdown of the bus system: in a first method step, a bussubscriber and/or the master module recognize(s) an error status, in asecond method step, the bus subscriber and/or the master moduletransmit(s) an emergency signal to all bus subscribers and to the mastermodule, in a third method step, a further bus subscriber receives theemergency signal, immediately forwards it to an adjacent bus subscriberand simultaneously evaluates it, and in a fourth method step, thefurther bus subscriber shuts itself down.

This has the advantage that all bus subscribers of the bus system areable to be shut down within a short period of time. The emergency signalmay not be fully evaluated right away but may simultaneously beforwarded to all bus subscribers and to the master module as soon as ithas been identified as an emergency signal.

The emergency signal may interrupt a data packet. This has the advantagethat the emergency signal is immediately sent to all bus subscribers andto the master module as soon as the error status has been identified.There may be no need to wait until the data packet has been transmittedin its entirety. As a result, a rapid shutdown of all bus subscribers ispossible, and the security is improved.

The transmission of the interrupted data packet may not be continued andthe interrupted data packet may be discarded. This has the advantagethat an error that occurs in the data packet due to the interruption hasno effect on the bus system. The security is therefore improved.

All data packets may have an identical length, in particular signallength, and the length of the emergency signal, in particular the signallength, may be shorter than the length of the data packets. This has theadvantage that the emergency signal is able to be transmitted fasterthan a data packet. As a result, the security is improved.

Two consecutive data packets may be temporally spaced apart from eachother by a transmission pause, and the emergency signal may interrupt atransmission pause. This has the advantage that the emergency signal maybe transmitted immediately and independently of the status of the dataline. The emergency signal may be transmittable at any time, regardlessof whether a data packet happens to be transmitted or a transmissionpause exists at the time when the emergency signal is transmitted.

The emergency signal may be shorter than the transmission pause.

The bus system may have two data lines, the bus subscriber and/or themaster module transmitting the emergency signal simultaneously with theaid of both data lines. This has the advantage that the emergency signalreaches all bus subscribers in a communications ring faster when it istransmitted with the aid of the two data lines in two oppositedirections than when the emergency signal is transmitted by only onedata line in one direction.

According to an example embodiment of the present invention, in a bussystem, in which a further bus subscriber is able to be integrated intothe bus system with the aid of a method for integrating a further bussubscriber as previously described, the bus system has a master moduleand bus subscribers, which are disposed in series, and the master moduleand the bus subscribers are connected to one another with the aid of atleast one data line.

This has the advantage that a further bus subscriber, in particular abus subscriber that needs a longer period of time for the activation, iseasily integratable into the bus system retroactively.

In the production mode, i.e. after a granted release, no bus subscribermay be admitted to the bus system.

The admittance to the bus system may be blocked with the aid of a bussubscriber disposed between the master module and the further bussubscriber so that the loading of the master module is reduced. Thisincreases the security.

The further bus subscriber may be automatically admitted to the bussystem in a new startup of the bus system.

The bus system may include at least one first data line and one seconddata line. This offers the advantage that a data packet is able to besent from the master module to the bus subscribers with the aid of thefirst data line, and a data packet is able to be sent from a respectivebus subscriber to the master module with the aid of the second dataline, in particular at the same time. The speed of the data transmissionis thus increased and the security improved. For the closing of the bussystem, the first data line may be connected to the second data line bythe last bus subscriber, in particular short-circuited. The first andthe second data line thus form a communications ring.

A data packet may be transmittable from the master module to the bussubscribers using the first data line. This has the advantage that thefirst data line and the second data line may be disposed in parallel.Data packets may be transmittable from the master module to the bussubscribers at any time with the aid of the first data line. As aresult, the data transmission from the master module to the bussubscribers will not be interrupted in order to transmit a respectivedata packet from an individual bus subscriber to the master module.

A respective data packet may be transmitted from an individual bussubscriber to the master module with the aid of the second data line.This has the advantage that the first data line and the second data linemay be placed in parallel. Data packets may be transmittable by arespective bus subscriber to the master module at any time via thesecond data line. As a result, the data transmission from the bussubscribers to the master module will not be interrupted in order totransmit a data packet from the master module to an individual bussubscriber.

The respective data line may have at least one data cable in each case,and each bus subscriber may be connected by a respective data cable tothe bus subscriber upstream or downstream from it or to the mastermodule. This has the advantage that the respective data line may have amodular configuration. As a result, a further bus subscriber is easilyconnected to the bus system with the aid of a further data cable.

Each data cable may have two mating plug connector parts and each bussubscriber may have a first plug connector part for the connection tothe respective upstream bus subscriber with the aid of an individualdata cable, and each bus subscriber may have a second plug connectorpart for the connection to the respective downstream bus subscriber.This has the advantage that the bus subscribers of the bus system areeasily connected to each other in a reversible manner. As a result, afurther bus subscriber is easily connectable to the bus system, or a bussubscriber is easily separated from its upstream bus subscriber and/orfrom its downstream bus subscriber.

The respective data cable of the first data line and the respective datacable of the second data line may be disposed between two adjacent bussubscribers in a cable sheath, the cable sheath in particularsurrounding the data cables in the circumferential direction, inparticular enveloping them. This has the advantage of reducing thewiring expense. The first and the second data line are advantageouslyconnected by a shared plug connector part so that only one plugconnector part has to be plugged into the bus subscriber in order toconnect a bus subscriber to its upstream or downstream bus subscriber.The plug connection may be implementable in a manner that prevents apolarity reversal.

A supply line and/or a ground lead for the bus subscribers may bedisposed in the cable sheath. This has the advantage of reducing thewiring expense. The data cables and the supply line and/or the groundlead may be connected to a shared plug connector part so that only oneplug connector part has to be plugged into the bus subscriber in orderto connect a bus subscriber to its upstream or downstream bussubscriber. The plug connection may be implementable in a manner thatprevents a polarity reversal.

Each bus subscriber may have a switch, which is connected to arespective data line, the switch being configured to interrupt the datatransmission along the respective data line. This has the advantage thatthe individual bus subscriber is configured to use the switch to stopdata packets that are not meant to reach the master module. In thismanner, the bus subscriber relieves the load of the master module.

Each bus subscriber may have a time-measurement device. This has theadvantage that the time-measurement device allows the individual bussubscriber to measure a time span within which a further bus subscriberresponds to a data packet, and in particular sends a further datapacket. Thus, the further data packet is able to be evaluated as afunction of this time span, and in particular is able to be blocked bythe switch. This relieves the loading of the master module.

Each bus subscriber may have a logic circuit, and the logic circuit inparticular may make it possible to evaluate data packets of the mastermodule and/or of the bus subscribers. This offers the advantage that theswitch and/or the time-measurement device is/are able to be actuatedwith the aid of the logic circuit, in particular as a function of a datapacket.

The respective logic circuit may have a storage device, which may beused for storing data packets. As a result, a data packet that wasstopped by a bus subscriber may be stored by its storage device and maybe transmitted to the master module and/or to a bus subscriber at alater point in time.

The logic circuit may be configured to evaluate the status of the bussystem, in particular to detect whether a release was granted for thebus system.

Each bus subscriber may have an electronic circuit, the electroniccircuit including the switch and/or the time-measurement device and/orthe logic circuit, the switch and/or the time-measurement device and/orthe logic circuit in particular being integrated into the electroniccircuit. This has the advantage that the electronic circuit may have acompact and secure configuration.

Further features and aspects of example embodiments of the presentinvention are described in greater detail below with reference to theappended Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a bus system according to an exampleembodiment of the present invention.

FIG. 2 shows the time characteristic of data packets on a data bus.

FIG. 3 shows the time characteristic of data packets and an emergencysignal on the data bus in a first case example.

FIG. 4 shows the time characteristic of data packets and an emergencysignal on the data bus in a second case example.

DETAILED DESCRIPTION

The bus system according to an example embodiment of the presentinvention has a master module M and bus subscribers (S1, S2, S3, S4),which are disposed in series and connected to one another. The bussystem has a first bus subscriber S1 disposed downstream from mastermodule M. The bus system has a second bus subscriber S2 downstream fromfirst bus subscriber S1, first bus subscriber S1 being situated upstreamfrom second bus subscriber S2. Second bus subscriber S2 is disposedupstream from a third bus subscriber S3, and third bus subscriber S3 issituated downstream from second bus subscriber S2. Third bus subscriberS3 is disposed upstream from a fourth bus subscriber S4, and fourth bussubscriber S4 is disposed downstream from third bus subscriber S3.

A bus subscriber (S1, S2, S3, S4) situated downstream from another bussubscriber (S1, S2, S3, S4) is situated at a greater distance frommaster module M in the direction of the series arrangement than theother bus subscriber (S1, S2, S3, S4). The other bus subscriber (S1, S2,S3, S4), which is disposed at a shorter distance from master module Mthan the bus subscriber (S1, S2, S3, S4) in the direction of the seriesarrangement, is located upstream from the bus subscriber (S1, S2, S3,S4).

For example, the bus system is an industrial plant which has variousdevices as bus subscribers (S1, S2, S3, S4), such as drives orelectronic components, e.g., drive converters for electric motors.

The data bus has a first data line 1 and a second data line 2, which ineach case serially connect the bus subscribers (S1, S2, S3, S4) andmaster module M to one another.

With the aid of first data line 1, master module M sends data packets(3, 4) such as control commands to the bus subscribers (S1, S2, S3, S4).With the aid of second data line 2, the bus subscribers (S1, S2, S3, S4)send data packets (3, 4) such as status information to master module M.

Each bus subscriber (S1, S2, S3, S4) has a first interface and a secondinterface, which may be arranged as a plug connector part in each case.Each data line (1, 2) has at least one data cable. Each data cable has afirst mating plug connector part and at least one second mating plugconnector part for a data transmission between the bus subscribers (S1,S2, S3, S4) along the respective data line (1, 2).

As a result, each bus subscriber (S1, S2, S3, S4) is able to beconnected to a second plug connector part of an upstream bus subscriber(S1, S2, S3, S4) using a first plug connector part and the respectivedata cable, and is able to be connected by a second plug connector partand the respective data cable to a first plug connector part of adownstream bus subscriber (S1, S2, S3, S4).

The respective data cable of first data line 1 and the respective datacable of second data line 2 may be guided in a shared cable sheath. Asupply line and/or a ground lead for the bus subscribers (S1, S2, S3,S4) may also be disposed in this cable sheath.

Each bus subscriber (S1, S2, S3, S4) has a switch, in particular as acomponent of an electronic circuit, which is connected to the respectivedata line (1, 2). The switch may be used to interrupt the datatransmission along the respective data line (1, 2).

Each bus subscriber (S1, S2, S3, S4) has a time-measurement device, inparticular a timer. The time-measurement device may be integrated intothe electronic circuit of the bus subscriber (S1, S2, S3, S4).

Using the electronic circuit, the data transmission along the respectivedata line (1, 2) is therefore able to be interrupted after a predefinedtime has elapsed.

Each bus subscriber (S1, S2, S3, S4) has a logic circuit. The logiccircuit may be integrated into the electronic circuit of the bussubscriber (S1, S2, S3, S4).

Using the logic circuit, data packets on the data bus are able to beevaluated, and the sender of a data packet, in particular, isidentifiable.

In the event that a bus subscriber (S1, S2, S3, S4) is inactive, a datapacket is forwarded without interruption and without a time delaythrough the inactive bus subscriber (S1, S2, S3, S4) to the downstreamor upstream bus subscriber (S1, S2, S3, S4). A data packet passesthrough an inactive bus subscriber (S1, S2, S3, S4) without obstruction.

The data bus may be implemented in a digital form.

For the initialization of the bus system, master module M sends arequest to the bus subscribers (S1, S2, S3, S4) situated downstream tolog in to master module M. An active bus subscriber (S1, S2, S3, S4)downstream from master module M logs in to master module M and forwardsthe request for the login to master module M to bus subscribers (S1, S2,S3, S4) disposed downstream from it. The logged in bus subscriber (S1,S2, S3, S4) then waits for a predefined period of time to see whether abus subscriber (S1, S2, S3, S4) downstream from it logs in to mastermodule M.

If no downstream bus subscriber (S1, S2, S3, S4) logs in to the mastermodule, then the last logged in bus subscriber (S1, S2, S3, S4) closesthe bus system as soon as the predefined period of time has elapsed, byconnecting first data line 1 and second data line 2 to each other, inparticular short-circuiting them. A data packet that is transmitted withthe aid of first data line 1 from master module M to the bus subscribers(S1, S2, S3, S4) is thus forwarded into second data line 2 at the finalbus subscriber (S1, S2, S3, S4) and routed back to the master module.

The last bus subscriber (S1, S2, S3, S4) is the particular bussubscriber (S1, S2, S3, S4) that logs in last to master module M and hasno downstream bus subscribers (S1, S2, S3, S4).

The request to log in to master module M is routed through an inactivebus subscriber (S1, S2, S3, S4) without this subscriber itself loggingin to master module M.

After the bus system has been closed, a release is granted by asuperordinate control or by an operator and the operation of the bussystem begins.

In the event that a bus subscriber (S1, S2, S3, S4) logs in late, i.e.after the predefined period of time following the login of the last bussubscriber (S1, S2, S3, S4) has elapsed, then this bus subscriber (S1,S2, S3, S4) sends a data packet to master module M. If a release wasalready granted, this data packet is stopped by an upstream bussubscriber (S1, S2, S3, S4) that is logged in to master module M andwill not be forwarded to master module M.

As soon as the release has been revoked, a data packet of the late bussubscriber (S1, S2, S3, S4) is forwarded to master module M and the latebus subscriber (S1, S2, S3, S4) is admitted to the bus system.

In the event that the late bus subscriber (S1, S2, S3, S4) has nodownstream bus subscribers (S1, S2, S3, S4) that are logged in to mastermodule M, then it becomes the new last bus subscriber (S1, S2, S3, S4)and closes the bus system after waiting out the predefined period oftime for the login of a bus subscriber (S1, S2, S3, S4).

The predefined period of time for the login of a bus subscriber (S1, S2,S3, S4) is able to be adapted to the bus subscribers (S1, S2, S3, S4).The period of time may be selected such that bus subscribers (S1, S2,S3, S4) that have a longer start-up time are securely logged in tomaster module M.

During the initialization of the bus system, bus addresses for the bussubscribers (S1, S2, S3, S4) are automatically assigned. For thispurpose, master module M sends the bus address “1” to first bussubscriber S1. First bus subscriber S1 logs in to master module M usingthis bus address and increments the bus address by 1 and forwards it tothe bus subscriber (S1, S2, S3, S4) disposed downstream. The downstreambus subscriber (S1, S2, S3, S4) logs in to master module M using theincremented bus address, i.e. bus address “2” in this instance,increments this bus address by 1 again and forwards it to the bussubscriber (S2, S3, S4) downstream from it.

In an effort to restrict the number of bus subscribers (S1, S2, S3, S4)in the bus system, a bus subscriber (S1, S2, S3, S4) that is given a busaddress that is greater than the maximally allowed number of bussubscribers (S1, S2, S3, S4), will not further increment this busaddress but forwards the same bus address to its downstream bussubscriber (S1, S2, S3, S4), which uses this bus address to log in tomaster module M. As soon as master module M receives a bus address thatis greater than the maximally allowed number of bus subscribers (S1, S2,S3, S4), master module M aborts the initialization of the bus system andtransmits an error report to a control superordinate to master module M.

If a bus subscriber (S1, S2, S3, S4) that is not yet active, i.e. aninactive bus subscriber (S1, S2, S3, S4), receives a bus address from abus subscriber (S1, S2, S3, S4) upstream from it or from master moduleM, then this bus address is looped through the inactive bus subscriber(S1, S2, S3, S4) without being incremented, and is assigned to adownstream bus subscriber (S1, S2, S3, S4).

FIGS. 2 through 4 show the time characteristic of data packets 3 thatare transmitted with the aid of a respective data line (1, 2). Each datapacket 3 has a predefined length that is a function of the number of bussubscribers (S1, S2, S3, S4) of the bus system.

The data transmission is interrupted for a predefined period of timebetween two temporally successive data packets 3, which means that twotemporally successive data packets 3 are temporally spaced apart withthe aid of a transmission pause 6.

As soon as a bus subscriber (S1, S2, S3, S4) or master module M detectsan error, data packet 4 transmitted at that instant is immediatelyinterrupted and an emergency signal 5 is transmitted by the respectivebus subscriber (S1, S2, S3, S4) or by master module M, as illustrated inFIG. 3. This emergency signal 5 causes an immediate shutdown of all bussubscribers (S1, S2, S3, S4).

The interrupted data packet 4 is immediately terminated and not furtherprocessed by the bus subscribers (S1, S2, S3, S4).

If a bus subscriber (S1, S2, S3, S4) or master module M detects an errorduring a transmission pause 6, then transmission pause 6 will beinterrupted and an emergency signal 5 be sent by the respective bussubscriber (S1, S2, S3, S4) or by master module M, as illustrated inFIG. 4. This emergency signal 5 causes an immediate shutdown of all bussubscribers (S1, S2, S3, S4).

The respective bus subscriber (S1, S2, S3, S4) transmits emergencysignal 5 on both data lines (1, 2). In other words, emergency signal 5is transmitted from the respective bus subscriber (S1, S2, S3, S4) inthe direction of master module M on the second data line and istransmitted by the respective bus subscriber (S1, S2, S3, S4) away frommaster module M on first data line 1.

The respective bus subscribers (S1, S2, S3, S4) immediately process theemergency signal 5 and at the same time forward it to the downstream bussubscriber (S1, S2, S3, S4) so that the bus subscribers (S1, S2, S3, S4)shut down immediately. In other words, emergency signal 5 is not firststored and processed but is immediately forwarded to all bus subscribers(S1, S2, S3, S4) and to master module M.

The emergency signal 5 may have a temporally shorter length than thedata packets (3, 4) and/or transmission pause 6.

LIST OF REFERENCE CHARACTER

M master module

S1 first bus subscriber

S2 second bus subscriber

S3 third bus subscriber

S4 fourth bus subscriber

1 first data line

2 second data line

3 data packet

4 data packet

5 emergency signal

6 transmission pause

What is claimed is:
 1. A method for operating a bus system that includesa master module and bus subscribers arranged in series and downstream ofthe master module, comprising: initializing the bus system, including:sending, by the master module, a request to the bus subscribers to loginto the master module; each active bus subscriber, in series order,logging into the master module after receiving the request, forwardingthe request to an immediately-adjacent downstream bus subscriber, andwaiting for a predetermined time period for the immediate-adjacentdownstream bus subscriber to log into the master module; and stoppingthe initializing after the predetermined time period has elapsed withouta bus subscriber logging into the master module and closing the bussystem to a further bus subscriber; after closing the bus system,sending a data packet by the further bus subscriber to the mastermodule; while the bus system is closed, stopping the data packet by abus subscriber that is logged into the master module and is locatedupstream from the further bus subscriber; after the bus system is nolonger closed, forwarding the stopped data packet to the master module,admitting the further bus subscriber to the bus system, and closing thebus system after the predetermined time period has elapsed without anadditional bus subscriber logging into the master module.
 2. The methodaccording to claim 1, wherein the initializing includes automaticallyassigning, by the master module, a bus address to each logged-in bussubscriber.
 3. The method according to claim 1, wherein the initializingincludes assigning a bus address to each bus subscriber, each bussubscriber incrementing its assigned bus address and forwards theincremented bus address to a downstream bus subscriber to assign theincremented bus address to the downstream bus subscriber.
 4. The methodaccording to claim 1, wherein the initializing is aborted if a number ofbus subscribers connected to the bus system exceeds a maximally allowednumber of bus subscribers.
 5. The method according to claim 1, whereinthe master module aborts the initializing if the master moduledetermines that a number of bus subscribers connected to the bus systemexceeds a maximally allowed number of bus subscribers.
 6. The methodaccording to claim 1, wherein the bus subscribers and master modulecommunicate with each other via a first data line and a second dataline.
 7. The method according to claim 6, wherein the master moduletransmits data packets to the bus subscribers via the first data line.8. The method according to claim 6, wherein the master module receivesdata packets from the bus subscribers via the second data line.
 9. Themethod according to claim 7, wherein the master module receives datapackets from the bus subscribers via the second data line.
 10. Themethod according to claim 1, further comprising closing the bus systemby a control device superordinate to the master module.
 11. The methodaccording to claim 1, further comprising revoking closure of the bussystem by a control device superordinate to the master module.
 12. Themethod according to claim 10, further comprising revoking closure of thebus system by a control device superordinate to the master module. 13.The method according to claim 6, wherein at least one of the data linesincludes at least one data cable.
 14. The method according to claim 6,wherein the master module and each bus subscriber includes a firstconnector connected to the first data line and a second connectorconnected to the second data line.
 15. The method according to claim 14,wherein the each data line includes a first connector plug partplug-connecting to a second connector plug part of the first connector.16. The method according to claim 1, wherein the bus subscribers includedrives, electronic components, and/or drive converters for electricmotors of an industrial plant.
 17. The method according to claim 1,further comprising forwarding, without interruption and without a timedelay, a data packet through an inactive bus subscriber.
 18. The methodaccording to claim 1, further comprising shutting down all bussubscribers in response to detection of an error by the master moduleand/or a bus subscriber.
 19. The method according to claim 18, whereinthe shutting down includes interrupting a currently-transmitted datapacket and transmitting an emergency signal.
 20. A bus system,comprising: a master module and bus subscribers arranged in series andconnected to each other via at least one data line; wherein the bussystem is adapted to perform the method recited in claim 1.